Contamination and risk assessment of heavy metals, and uranium of sediments in two watersheds in Abiete-Toko gold district, Southern Cameroon

Eugène Pascal Binam Mandeng; Louise Marie Bondjè Bidjeck; Armel Zacharie Ekoa Bessa; Yvan Demonstel Ntomb; Jacques Wassouo Wadjou; Elvine Paternie Edjengte Doumo; Lucien Bitom Dieudonné

doi:10.1016/j.heliyon.2019.e02591

Contamination and risk assessment of heavy metals, and uranium of sediments in two watersheds in Abiete-Toko gold district, Southern Cameroon

Heliyon. 2019 Oct 5;5(10):e02591. doi: 10.1016/j.heliyon.2019.e02591. eCollection 2019 Oct.

Authors

Eugène Pascal Binam Mandeng^{1

2}, Louise Marie Bondjè Bidjeck², Armel Zacharie Ekoa Bessa², Yvan Demonstel Ntomb², Jacques Wassouo Wadjou¹, Elvine Paternie Edjengte Doumo³, Lucien Bitom Dieudonné^{2

4}

Affiliations

¹ Centre for Geological and Mining Research, Garoua, Cameroon.
² Department of Earth Sciences, University of Yaoundé I, Yaoundé, Cameroon.
³ Department of Earth Sciences, Faculty of Science, University of Ngaoundere, Cameroon.
⁴ Faculté d'Agronomie et des Sciences Agricoles, University of Dschang, Cameroon.

Abstract

In this investigation, the level of toxic metals (Cd, Pb, Hg, Cu, Ni, Al, Zn and U) was determined in sediment samples from two watersheds (Kienké and Tchangué) in the Abiete-Toko gold district, southern Cameroon. The potential contamination and toxicity of studied metals was determined by evaluating enrichment factor (EF), geo-accumulation index (Igeo) and ecological risk assessment (ERA). Considering the spatial distribution patterns, metal concentrations were lower than the average shale values, except for Cu and Ni of site 4 in the Kienké watershed and only Ni in the Tchangué watershed. In this study, the EF and Igeo values revealed that sediments were moderately polluted by Ni and Cu and unpolluted by other metals. The evaluation of the ERA based on ecological risk index (RI), ecological risk factor (Er), contamination factor (CF) and pollution load index (PLI) revealed that the sediments from the Abiete-Toko watersheds have significant to very high ecological risk assessment and are generally unpolluted by trace metals and U, except for Ni and Cu. Little quantities of heavy metals with low U levels and distribution were found at the sites close to the vicinity of artisanal mining and peri-urban areas. This proximity reveals that artisanal gold mining activities, agricultural runoff, and other anthropogenic inputs in the study area are probable sources of slight metal contamination. However, the non-use of toxic effluents for gold mining and pesticides for agriculture can be an advantage of the unpolluted status of the watersheds. The physical degradation of the ecosystem through excavations, wells and other stream diversion methods is expanding in the zone. Appropriate measures should be taken by artisans to rehabilitate the gold mining sites, to ensure appropriate treatment of wastewater and non-use of toxic effluents into nearby tributaries.

Keywords: Abiete-toko watersheds; Applied ecology; Contamination; Ecological risk assessment; Enrichment factor; Environmental assessment; Environmental impact assessment; Environmental radioactivity; Environmental risk assessment; Geo-accumulation; Sediments; Soil pollution; Waste treatment.